Vapor separating pump



May 21, 1963 M. L. EDWARDS VAPOR SEPARATING PUMP Filed Sept. 21, 1959 INVENTOR. MILES LOWELL EDWARDS ATTORNEYS United States Patent 3,090,321 VAPOR SEPARATING PUMP Miles Lowell Edwards, 13191 Sandhurst Place, Santa Ana, Calif. Filed Sept. 21, 1950, Ser. No. 841,094 4- Claims. (Cl. 103-113) This invention relates to a vapor separating pump and has particular reference to a new and improved form and arrangement of diffuser passages or openings which serve as vapor discharge outlets at low rates of flow and as secondary or auxiliary inlets at high rates of flow.

In an aircraft fuel booster pump, for example, the fuel requirements and operating characteristics vary widely under different flight conditions. Diffuser passages adjacent the pump inlet which are normally intended to function as vapor outlet openings may, if properly designed and arranged, experience a reversal of flow which may be used toadvantage to augment or supplement the flow through the main pump inlet flight conditions when the highest possible rate of flow is demanded.

At high altitudes where jet engines operate most efficiently and in level flight at cruising speed and under other conditions where the engine demand is reduced, flow velocities through the pump are reduced accordingly.

At reduced discharge the rotary motion of the pump impeller increases the rotative speed of the liquid as it is engaged by the entrance portions of the impeller creating the usual air or vapor binding problem which is alleviated to considerable extent by the conditional diffuser passages. Such a relatively high rotating velocity of the a liquid generates values of centrifugal force in the liquid which produce an outward flow through the diffuser passages. The reduced flow or delivery velocity provides a time delay within the impeller which allows more time for the centrifuging of bubbles and the merging 5 of many small bubbles into a fewer number of large ones which are swept out with a considerable amount of liquid through the diffuser passages. As the flow through the pump decreases in proportion to the full capacity of the pump, the centrifugal and vapor sweeping 1 factors near the pump entrance becomes increasingly active to prevent air or vapor binding. This is the normal function of diffuser passages which operate quite effectively in conventional pumps to evacuate such bubbles from the pumping chamber.

However, when the aircraft is climbing rapidly from the ground or other relatively low altitude, different conditions obtain and different requirements exist. At such times the pump is discharging at, or close to, its capacity in order to deliver fuel to the engine at a maximum rate. The velocity of fuel through all pump passages is very high and there is relatively little rotation of the fuel at the entrance portion of the impeller, the velocity being primarily in an axial direction through the impeller and pumping chamber. At such high rates of flow, and particularly at lower altitudes, little or no vapor separation occurs and the pump is able to swallow the gases and vapors and force them through the fuel system at such high rates that they cannot accumulate to form a pocket or trap within the pump. Air or vapor binding does not present a problem under such flight conditions. The high velocity axial flow does not have sufiicient rotation to be centrifu-gally discharged outwardly through the diffuser passages whereby a reduction in pressure is cre ated in the pump inlet, tending to draw additional liquid inwardly into the pump through the diffuser passages.

thus, the diffuser passages may be utilized to function as auxiliary inlets which may appreciably increase the normal capacity of the pump when it is most needed because at such times the diffuser passages are not required to relieve gas and vapor binding. Heretofore, however, the diifuser passages have been designed only to relieve gas and vapor binding and have not been designed to function effectively, if at all, as secondary inlets.

In accordance with the present invention, the diffuser passages are shortened to form mere openings and are provided with walls which approximate tangential directions 'both in the direction of rotation of the impeller and in the counter-direction to facilitate the intake of fuel along one of these walls under one condition of operation and to facilitate the discharge of gas and vapor bubbles along the opposite wall under the other operating condition explained above. These walls intersect the inside surface of the impeller chamber at approximately equal and small acute angles to provide in relatively sharp edges to guide the flows in both directions and avoid any obstructing or deflecting surfaces or contours which would tend to impede the flows. When the diffuser passages or openings are made in such shape, they serve the dual purpose more effectively than diffuser passages heretofore provided.

The general object of the present invention is, there fore, to provide an improved form and arrangement of diffuser outlets adjacent the inlet of a pump which will act with improved effectiveness as secondary inlets at high rates of flow through the pump.

Another object is to provide openings adjacent the inlet of a pump with wall configurations to facilitate flows in opposite directions through such openings under different operating conditions.

Another object is to provide improved difluser outlets in a pump.

Additional objects and advantages will become apparent and the invention will be better understood from the following description of the preferred embodiment illustrated on the accompanying drawing. It is to be understood, however, that the invention is capable of variations and modifications without departing from the spirit of the invention as defined in the appended claims.

In the drawings:

FIGURE 1 is a fragmentary longitudinal sectional view showing a booster pump embodying the features of the invention mounted in an aircraft fuel tank;

FIGURE 2 is an enlarged cross sectional view on the line 2-2 of FIGURE 1; and

FIGURE 3 is a fragmentary side view of one of the diffuser openings.

The numeral 10 designates the bottom wall of a fuel tank or cell having an opening 11 in which the pump 12 is mounted. The pump 12 includes a housing 13 containing in its upper portion an electric motor 14 having an armature shaft 15 mounted at its lower end in a suitable bearing 16 for driving the pump impeller 17. Housing 13 is equipped with a plurality of legs 18 connected with a mounting flange 19. The arrangement is such that housing 13 and legs 18 are insertable through tank opening 11 with the mounting flange 19 underlying the bottom of the tank about the opening 11. Flange 19 is secured to the tank by screws 20 having threaded engagement with an oval mounting ring 21 inside the tank. Numeral 22 designates a gasket between flange 1'9 and the tank.

A bottom plate 25 provides a sump slightly below the level of the bottom wall of the tank. Bottom plate 25 is connected with flange 19 by screws 26 and the sump is enclosed by a cylindrical screen 27. Connected to the lower end of housing 13 is a tapered and generally conical housing part 28, forming with the impeller 17 a pumping chamber. The lower end of housing part 28 is outwardly flared at 29 to provide an inlet opening 30 on the approximate level of the tank bottom just 3 above the sump in bottom plate 25. A volute discharge chamber 31 is in annular communication with the upper end of the pumping chamber for tangential discharge into a discharge connection 32. An outlet pipe 33 is connected to discharge connection 33 exterior to the tank by means of a long screw 34.

Although a vertical pump is illustrated by way of example, the present invention is not limited to a vertical pump as the features of novelty presently to be described are equally effective in pumps mounted horizontally or in inclined positions.

In the present instance, the impeller 17 comprises a solid center cone 35 equipped with a single spiral corkscrew vane 36 which fits the taper of housing part 28 with close running clearance. Vane 36 terminates at its lower end in a generally radial entering edge 37 which rotates in the smallest diameter portion of housing part 23 immediately above and inside the inlet opening 39. The invention is not limited to this particular form of impeller, however, but may be used with other impellers which rotate the entering liquid as described herein.

A plurality of diffuser openings 40 is circumferentially spaced around the housing part 28 just above the lowermost peripheral edge of the impeller vane 36 so as to be swept by the impeller. Asshown in FIGURE 2, each opening 40 has an approximately tangential wall 41 on its leading side and an approximately tangential wall 4-2 on its trailing side with reference to the direction of rotation of the impeller designated by the ar row 43. The tangential inclination of walls 41 and 42 results in sharp edges 44 where these Walls break through the inside surface of the pumping chamber. The inclination of walls 41 and 42 also inherently provides enlarged openings through the outer wall of housing part 28.

The shape of the wall surfaces on the upper and lower sides of openings 40 is not critical but, for convenience in manufacture, these openings are preferably made circular with a rotary tool such as a drill bit or reamer whereby in the illustrated embodiment the walls 41 and 42 are opposite sides of a single conical wall which provides symmetry in all radial directions as seen in H6- URE 3. The sloping tangential walls 41 and 42 may extend to the outer surface of housing part 28 but, in the present instance to avoid weakening the housing part, these walls terminate at a cylindrical surface 45 corresponding to the diameter of the 'reamer. The diameter of the outer part of the opening 45 is so much larger than the diameter of the opening 40 in the inside surface of the pumping chamber that the approximately radial directions of surface 45 on the leading and trailing sides of the opening as viewed in FIGURE 2 do not obstruct tangential flows as above described along the Walls 41 and 42.

When the diffuser openings are formed in the manner described it is advantageous to make housing 28 of thin Wall section as shown so that the cylindrical bores 45 will not be deep in relation to their diameter, but the broad principles of the invention may also be applied to thick wall sections when desired. As shown, the diameter of bores 45 greatly exceeds the thickness of the wall section.

When the flow through the pump is considerably less than its capacity output, the velocity through the pumping chamber is proportionately reduced and there is a corresponding and inversely related increase in the rotative speed of the liquid as it becomes enclosed between the surfaces of the rotating vane 36. This increase of rotating liquid speed increases the centrifugal force outwardly in the liquid to bring about an outward flow of liquid through the openings 40 along the tangential walls 52 as indicated by the arrow 52. Under this condition of operation the time delay of the liquid within the pumping chamber allows time for the centrifuging of bubbles and the merging of small bubbles into larger ones so that the bubbles are swept outwardly through openings 4%) before they are carried along with the main how. 7 This is the normal mode of operation of tangential diifuser passages in prior pumps to prevent air or vapor binding under low flow conditions.

At high entrance velocity corresponding to near pump capacity delivery, the incoming liquid does not remain in the entrance portion of the impeller long enough to be rotated at high speed in this region and so it is not centrifugally discharged outwardly through the openings 4%. Such high entrance velocity of the liquid in an axial direction then creates a reduction in pressure at the openings 4t) drawing liquid inwardly into the pump as indicated by arrow 51 in addition to that drawn in through the main inlet 36. At high rates of flow there is a minimum centrifugal force effect and a minimum time delay within the impeller to cause centrifugal separation and the gathering of large gas bubbles. The bubbles are swallowed up in the main flow and discharged through the line without causing gas or vapor binding. Under such conditions the tangential wall surfaces 41 guide the auxiliary inlet flows 51 in tangential directions into the pumping chamber to facilitate to the maximum the increase in delivery that may be derived from the dual use of the diffuser openings.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

1. In a vapor separating and mixed flow submersible pump, an impeller rotatable on an axis of rotation and having an axial inlet eye, a housing having walls forming a pumping chamber, said housing having an inlet communicating with said impeller eye along the line of the axis rotation of said impeller, said impeller having an entrance end adjacent said inlet, said housing having circumferentially spaced openings surrounding the entrance end of the impeller and outwardly divergent wall surfaces forming opposite leading and trailing sides of said openings directed approximately tangentially to the impeller, said surfaces intersecting the inside surface of said chamber at small acute angles forming sharp edges at the inner ends of the openings to flow gas out of the chamber at low flow rates and to flow liquid into the chamber at high flow rates, and means for mounting said pump with said openings and inlet submerged in a body of liquid to be pumped.

2. The pump of claim 1 wherein said acute angles are equal.

3. The pump of claim 1 wherein said divergent wall surfaces are frusto-conical.

4. The pump of claim 1 wherein said openings have cylindrical outer ends intersecting the outer surface of said housing.

References Cited in the file of this patent UNITED. STATES PATENTS 

1. IN A VAPOR SEPARATING AND MIXED FLOW SUBMERSIBLE PUMP, AN IMPELLER ROTATABLE ON AN AXIS OF ROTATION AND HAVING AN AXIAL INLET EYE, A HOUSING HAVING WALLS FORMING A PUMPING CHAMBER, SAID HOUSING HAVING AN INLET COMMUNICATING WITH SAID IMPELLER EYE ALONG THE LINE OF THE AXIS ROTATION OF SAID IMPELLER, SAID IMPELLER HAVING AN ENTRANCE END ADJACENT SAID INLET, SAID HOUSING HAVING CIRCUMFERENTIALLY SPACED OPENINGS SURROUNDING THE ENTRANCE END OF THE IMPELLER AND OUTWARDLY DIVERGENT WALL SURFACES FORMING OPPOSITE LEADING AND TRAILING SIDES OF SAID OPENINGS DIRECTED APPROXIMATELY TANGENTIALLY TO THE IMPELLER, SAID SURFACES INTERSECTING THE INSIDE SURFACE OF SAID CHAMBER AT SMALL ACUTE ANGLES FORMING SHARP EDGES AT THE INNER ENDS OF THE OPENINGS TO FLOW GAS OUT OF THE CHAMBER AT LOW FLOW RATES AND TO FLOW LIQUID INTO THE CHAMBER AT HIGH FLOW RATES, AND MEANS FOR MOUNTING SAID PUMP WITH SAID OPENINGS AND INLET SUBMERGED IN A BODY OF LIQUID TO BE PUMPED. 